WATER REPELLENT ORTHOPEDIC DRESSING

Abstract: The present invention provides a water repellant dressing which is made from a soft, smooth, conformable, air-permeable, hydrophobic fabric. The fabric contains polymeric fibers of an extruded blend of a polymer and a fluorochemical oxazolidinone. These extruded fibers may be used to make a nonwoven, knitted or woven fabrics. The dressings of the present invention are especially useful when in contact with skin because the dressings are water repellant and soil resistant but allow air and vapor to pass through the dressings.

Description: WATER REPELLENT ORTHOPEDIC DRESSING CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. patent application Serial Number 08/069,868 filed June 1, 1993, which is a continuation-in-part of U.S. patent application Serial Number 07/703,038 filed May 17, 1991, pending, which is a continuation of U.S. patent application Serial Number 07/242,120 filed September 9, 1988, abandoned. BACKGROUND The present invention generally relates to medical dressings and particularly relates to orthopedic dressings, such as padding and stockinettes, which are used with casting material. The dressings of the present invention are especially useful when in contact with skin because the dressings are water repellent and soil resistant but allow air and vapor to pass through the dressings. Processes to prepare the materials used to make the dressings of this invention are described in the copending U.S. patent application Serial Number 07/703,038 filed May 17, 1991 which is incorporated by reference herein. SUMMARY OF THE INVENTION The present invention provides a water repellent orthopedic dressing. The dressing is made from a soft, smooth, conformable, air-permeable, hydrophobic fabric. The fabric contains polymeric fibers of an extruded blend of thermoplastic polymer and a fluorochemical oxazolidinone. These extruded fibers may be used to make a nonwoven fabric which is particularly suited for use in cast or splint padding. Alternatively, the fibers may be spun into yarns which may be used to make knitted or woven fabrics. A knitted fabric made from the extruded fibers is particularly suited for use in stockinettes and tubular stockinettes. Unexpectedly, the dressings made of the present extruded fibers are significantly softer, smoother and more conformable when compared to similar dressing that are surface only treated with water repellent materials such as fluorochemicals as described in U.S. Patent 4,989,593. The enhanced tactile properties of the present dressings provide water repellent fabrics which may be in direct contact with a patient's skin and provide both increased comfort to the patient and reduced irritation to the skin. In addition, the processability and/or performance of the extruded fibers may be enhanced by surface treating or coating the fibers with a hydrophilic antistatic lubricant and a fluorochemical water repellent. In the embodiment of the invention, the hydrophilic lubricant aids processing of the fibers while the fluorochemical water repellent gives improved initial water resistance. Preferred thermoplastic polymers which are used to make the present fibers include polyethylene, polypropylene and polyesters such as polyethylene terephthalate as well as blends or copolymers thereof. Particularly preferred polymers melt at sufficiently low temperatures to allow melt blending of the polymer with a fluorochemical oxazolidinone without degradation of the oxazolidinone. Alternative polymers include low melting non-reactive compatible polymers. Polyethylene and polypropylene are presently most preferred polymers. Suitable oxazolidinones are described in U.S. Patents 5,025,052 and 5,099,026, which are incorporated by reference herein. A preferred fluorochemical oxazolidinone (available from 3M, St. Paul, MN) is schematically represented by the formula This preferred oxazolidinone (referred to herein as ODOX) is prepared according to reported methods. Briefly, a perfluoroalkylsulfonamide, C 8 F 17 SO 2 N(CH 3 )H, is reacted with epichlorohydrin to provide the chlorohydrin, C 8 F 17 SO 2 N(CH 3 )CH 2 CH(CH 2 Cl)OH. The chlorohydrin is then reacted with an octadecylisocyanate, Cι 8 H 37 NCO, to provide an intermediate urethane which cyclizes in the presence of base to provide the oxazolidinone listed above. To prepare fibers for use in this invention, the polymer and fluorochemical oxazolidinone are melt blended and then extruded into fibers using known apparatus and processes to provide fibers having between about 0.1-10.0 wt. % oxazolidinone, and more preferably between about 0.3-3.0 wt. % oxazolidinone. These fibers may then be used to prepare nonwoven, woven or knitted fabrics using known procedures. In addition, extruded fibers which have been crimped and oven-dried may be coated with a mixture of antistatic lubricant and fluorochemical water repellent and then cut into staple fibers to be used to prepare nonwoven, woven or knitted fabrics using known procedures. DETAILED DESCRIPTION Orthopedic casts and splints may be made from a water curable resin impregnated casting material that is used in combination with a soft layer of padding applied between the load-bearing casting material and a patient's skin. The padding is used to provide cushioning and protection to the skin and is preferred to be comfortable, easy to apply, non-irritating as well as quick drying. When a cast is made, generally a stretchy knit tubular stockinette is applied over a patient's limb, a padding is then wrapped over the stockinette, and the casting material is then applied over the cast padding. When a splint is made, a layer of padding alone is typically used.. In the present specification, the following terms are defined as follows. "Water Repellent" means the ability of a fabric to cause water to bead or be repelled from a surface as well as causing water which is mechanically or otherwise forced into the fabric to readily run out, leach out or be removed from the interstices of the fabric. "Conformability" means the ability of a fabric to easily or readily deform around an object. A quantitative measure of conformability is provided by the HANDLE-O-METER stiffness test set out in Example 2, below. "Smooth" means the tactile feel or texture of the surface and may be comparatively measured using a surface friction test set out in Example 3, below. "Soft" means the subjective tactile sensation of the fabric on the skin. Comparative softness of the present invention in relation to other water repellent fabrics or dressings is described in Example 4, below. "Hydrophobic" is a measure of the ability of the fabric to hold or absorb water on the fabric surface. A measure of hydrophobicity is provided by a measurement of a material's surface energy which is readily determined using the modified AATCC Test Method 118-1983 set out in U.S. Patent 5,027,803. Preferred dressings of this invention have surface energies less than about 40 erg/cm 2 and more preferably less than about 30 erg/cm 2 . Suitable fluorochemical water repellents for use in the present invention are those used in the manufacture of textile articles. In the manufacture of textile articles, such as carpet and apparel, or for example, other fibrous substrates such as paper and leather, it is common to treat such substrates with fluorochemicals to impart oil and water repellency to the surface of such materials. Suitable fluorochemicals for this use and their application to fibrous substrates are described in various publications, e.g., U.S. Patent Nos. 2,803,615 (Ahlbrecht et al.), 2,934,450 (Brown), 3,068,187 (Bolstad et al.), 3,094,547 (Heine), 3,329,661 (Smith et al.), 3,341,497 (Sherman et al.), 3,398,182 (Guenthner et al.), 3,458,571 (Tokoli), 3,462,296 (Raynolds et al.), 3,574,791 (Sherman et al.), 3,728,151 (Sherman et al.), 3,896,251 (Landucci), 3,916,053 (Sherman et al.), 4,013,627 (Temple), 4,024,178 (Landucci), 4,029,585 (Dettre), 4,034,964 (Sherman et al.), 4,144,367 (Landucci), 4,160,777 (Loudas), 4,165,338 (Katsushima et al.), 4,190,545 (Marshall), 4,215,205 (Landucci), 4,264,484 (Patel), 4,325,857 (Champaneria et al.), 4,340,749 (Patel), 4,401,780 (Steel), 4,426,476 (Chang), 4,525,305 (Patel), 4,525,423 (Lynn et al.), 4,529,658 (Schwartz et al.), 4,540,497 (Chang et al.), 4,560,487 (BrinMey), 4,564,366 (Patel), 4,565,641 (Chang et al.) 4,566,981 (Howells), 4,579,924 (Schwartz et al.), 4,582,882 (Lynn et al.), 4,606,737 (Stern), 4,668,406 (Chang), 4,668,726 (Howells) and Banks, R. E., Ed., "Organofluorine Chemicals and their Industrial Applications", Ellis Horwood, Ltd., West Sussex, England, 226-230 (1979). The preferred fluorochemical water repellent is SCOTCHGARD brand carpet protector (FC-359) an aqueous emulsion of a fluorinated polycarbodiimide of the type described in U.S. Patent 4,560,487, a fluorinated emulsifier, CH 3 I C 8 F 17 S0 2 N (CH 2 ) 2 N (CH 3 ) 3 C1 and a fluorochemical copolymer of the type generally described in U.S. Patent 3,916,053 and more specifically described in U.S. Patents 3,574,791 and 3,728,151. Suitable hydrophilic lubricant antistatic agents for use in the invention are any such agents conventionally used in the fiber industry such as Sipo Lube GS-1031, Synthetic Industries, Inc., Chickamauga, GA. The following examples provide preferred methods and procedures for practicing the present invention. These examples further illustrate various embodiments of the present invention and should not be construed to limit the scope of the invention which is set out in the appended claims. Example 1 - Fiber Preparation A polypropylene/oxazolidinone concentrate was made using a 40 mm twin screw extruder (Bestorff, Charlotte, NC) from virgin polypropylene (90 wt. % polypropylene, #3661-Fiber Grade, Fina Oil & Chemical Co., Dallas, TX) and a fluorochemical oxazolidinone (10 wt. % oxazolidinone, ODOX described above, Protective Chemicals Division, 3M, St. Paul, MN). The resulting polypropylene/oxazolidinone concentrate (10 wt. %) was metered into a 160 mm barrier-type double flight extruder with additional polypropylene (90 wt. %, #3661-Fiber Grade, Fina Oil & Chemical Co.), and the blend was melted with mixing at about 232-249°C for about 1-3 minutes. The melted mixture of polypropylene and oxazolidinone was extruded into 3 denier fibers. The extruded fibers were crimped, oven dried and cut to staple fibers of 3.81 cm or 4.76 cm in length. A fluorine analysis of the staple fibers indicated that the fluorochemical content of the fibers was between about 0.88-1.2 wt. %. This measurement provides an index of the amount of fluorine present on a fiber. Briefly, organic fluorine is converted to inorganic fluoride ion by burning a test sample in a sealed polycarbonate flask, via an electronic ignition system, in the presence of oxygen and a known volume of deionized water. The inorganic fluoride ion is absorbed into the water. The fluoride ion is measured using a fluoride ion specific electrode, Model #94-09 Fluoride Ion Electron commercially available from Orion Research Inc., Boston, MA. The shorter 3.81 cm extruded fibers were then processed into nonwoven cast padding using standard methods by Astro-Form Corporation, Danielson, CT, using commercially available Randoweb Equipment. Padding rolls 7.62 cm and 10.16 cm wide were also prepared and evaluated. The extruded polypropylene/oxazolidinone fiber padding had a lower than normal, compared to untreated polyester padding (Synthetic Cast Padding, MW 03, 3M, St. Paul, MN), tear strength as determined by manually tearing the fabric presumably because of the fiber length. The coextruded padding was very soft, conformable and had a very good resistance to water. When 4.76 cm extruded fibers were used to make a padding the tear strength was equivalent to that of the untreated polyester padding. The longer 4.76 cm extruded fibers were spun into 20 (cotton count) single yam using well-known processes by Doran Textiles, Shelby, GA. The yam was then knitted into stockinette rolls 5.08 cm and 7.62 cm wide by Balfour, Inc., Rockwood, TN, using commercially available circular Rib-Knit Equipment. The polypropylene/oxazolidinone stockinette was also very soft, conformable and had a very good resistance to water. Example 2 - Conformability Test This test measured the stiffness or hand of a nonwoven fabric. Conformable fabrics were more flexible and less stiff when compared to fabrics which were not as conformable. To measure the stiffness of a nonwoven fabric, the nonwoven material was deformed through a restricted opening using a plunger and the force required to do this was measured using the INDA Standard Test, HANDLE-O-METER Stiffness Test, 1ST 90.3 - 92 following reported procedures. The conformability was measured for three different paddings. An extruded polypropylene/oxazolidinone padding was prepared from 3.81 cm fibers according to Example 1. Surface treated padding was prepared using standard polyester padding (Synthetic Cast Padding, MW 03, 3M, St. Paul, MN) that was dipped in a 2 wt. % aqueous fluorochemical solution (FC-270 fluorochemical water repellent, 3M, St. Paul, MN). The excess fluorochemical solution was removed by wringing between two rollers and the surface treated padding was then dried in an oven at 65.6°C for about 24 hours. Untreated polyester padding was a commercially available standard polyester padding (Synthetic Cast Padding, MW 03, 3M, St. Paul, MN). The conformability data measured for the three paddings (samples evaluated were 7.62 cm x 15.24 cm) are provided in Table 1, below. The data (the average force calculated from three runs) indicate that the extruded polypropylene/oxazolidinone padding was more conformable when compared to a padding that was surface treated with only a fluorochemical water repellent. TABLE 1 PADDING AVERAGE FORCE untreated polyester 28.5 g surface treated polyester 46.5 ε extruded polypropylene/oxazolidinone blend 31 g Example 3 - Surface Friction Test This test measured the surface friction of a sample which may be used to evaluate the feel of the fabric. The test involves pulling a stainless steel boat covered with TRANSPORE tape (3M, St. Paul, MN) across a surface of the sample and measuring the force required to move the boat. The more force required to move the boat across the sample, the greater the surface friction of the sample. The requisite details for performing this test are described in U.S. Patent 4,667,661. The surface friction was measured for both nonwoven padding and knitted stockinettes. The extruded padding and stockinette were prepared according to Example 1, above. The surface treated padding and stockinette were prepared as described in Example 2. The untreated Synthetic Cast Padding, MW 03, and untreated MS 03 stockinette were both available from 3M, St. Paul, MN. The data measured for the different materials are provided in Table 2, below. The data (the average force calculated from three runs) indicate that the extruded polypropylene/oxazolidinone padding and stockinette both had greater surface friction when compared to the corresponding padding or stockinette that was surface treated with water repellent material prepared according to Example 2. TABLE 2 AVERAGE FORCE TO PADDING MOVE BOAT untreated polyester 68.25 g surface treated polyester 85.19 g extruded polypropylene/oxazolidinone blend 58.10 g STOCKINETTE , untreated polyester 76.51 g surface treated polyester 80.71 g extruded jolypropylene/oxazolidinone blend 63.80 g Example 4 - Softness Test This example provided the results of a test panel that subjectively evaluated and compared the softness of different padding and stockinette materials. In this example, three padding materials (an extruded polypropylene/oxazolidinone padding, a surface treated padding, and an untreated padding prepared according to Example 3) and three stockinettes (a stockinette made with extruded polypropylene/oxazolidinone fabric, a surface treated stockinette, and an untreated stockinette also prepared according to Example 3) were evaluated. Briefly, each evaluator was asked to rank the padding or stockinette material in order of softness. The identity of the materials was not provided to the evaluators. After the materials were ranked, the evaluators were then asked to assign a softness value to the material using a softness scale of 1-20, with a value of 1 being the softest and comparable to the softness of a cotton ball. The results of this evaluation are listed in Tables 3 and 4. TABLE 3 Padding Softness Test Softness Softness Softness Softness Softness Softness Rank Value Rank Value Rank Value Evaluator first 1-20 second 1-20 third 1-20 1 C 1 B 2 A 15 2 C 1 B 3 A 10 3 C 10 B 14 A 19 4 C 5 B 10 A 20 5 C 2 B 4 A 10 6 C 2 B 5 A 10 7 C 2 B 3 Al 15 average 3.29 5.86 14.14 value Materials: A - surface treated polyester padding B - extruded polypropylene/oxazolidinone padding C - untreated polyester padding (MW 03 padding) TABLE 4 Stockinette Softness Test Softness Softness Softness Softness Softness Softness Rank Value Rank Value Rank Value Evaluator first 1-20 second 1-20 third 1-20 1 A 4 C 6 B 10 2 A 2 C 3 B 15 3 A 8 C 12 B 18 4 A 5 C 10 B 15 5 A 5 C 10 B 15 6 A 3 C 10 B 15 7 A 5 C 8 B 10 average 4.57 8.43 14.0 value Materials: A - untreated polyester stockinette (MS 03 stockinette) B - surface treated polyester stockinette C - extruded polypropylene/oxazolidinone stockinette The data in Tables 3 and 4 indicate that the extruded padding and stockinette are significantly softer than a surface treated padding or stockinette. Example 5 - Extruded Polypropylene/Oxazolidinone Splint Padding Multi-layer immobilization splints were constructed and evaluated for water absorption and water retention. Briefly, the bottom layer of each splint was a 30.48 cm long and 8.89 cm wide padding made either from needle-tacked polypropylene/oxazolidinone fibers (99.3 wt. % polypropylene, 0.7 wt. % oxazolidinone, ODOX described above, 3M, St Paul, MN) or from needle-tacked untreated polypropylene fibers. Needle-tacking was carried out using a Hunter Needletacker (Morse and Berkshire Company, North Adams, MA). Both of the above fibers were needle tacked into nonwoven felts of about 340.2 g per 0.84 square meters. A strip of 1.27 cm transfer tape No. 950 (3M, St. Paul, MN) was adhered to the long edges of the padding and a strip of 3.81 cm transfer tape No. 927 (3M, St. Paul, MN) was adhered to the short edges of the padding. Next, eight layers of 25.4 cm long and 7.62 cm wide resin impregnated SCOTCHCAST 2 brand fiberglass casting tape (3M, St. Paul, MN) was centered on the layer of padding. Finally, a layer of commercially available spun-laced, hydroentangled nonwoven polyester fabric (SONTARA 8000, DuPont, Wilmington, DE treated with 2% fluorochemical water repellant, FC- 270, as described in U.S. Patent 5,027,803) was adhered to the padding layer using the transfer tapes. The water absorption and retention was determined for each splint. The splints were weighed dry, placed in a pan of water and immersed for 0.5 minute (holding the splint under water if necessary) while squeezing twice, removing the splint from the water, squeezing the splint twice using two hands, then weighing again. Each splint was set in a dry pan to cure and allowed to air dry for 5 hours and weighed again. When cured, the multiple layers of the splint bonded together to form a cohesive laminate and the extmded polypropylene/oxazolidinone padding was softer and smoother when compared to the untreated padding. The splint also had desirable water absorption and retention properties. TABLE 5 Splint Padding Water Absorped (%) After 5 Hours - Retained ( ) 1.875 inch (4.7625 cm) 67 55 polypropylene/oxazolidinone fibers needle-tacked at 128 needles/in 2 3.25 inch (8.255 cm) polypropylene 72 61 fibers needle-tacked at 128 needles/in 2 Percent water absorped or retained was calculated using the formula (wet splint-dry splint) x 100 dry splint Example 6 - Lubricated Water Repellent Fibers Using the method and materials described in Example 1, 4364 kg of polypropylene and 1091 kg of a mixture of 90% polypropylene and 10% fluorochemical oxazolidinone was mixed to give a 98/2 polypropylene/oxazolidinone mixture which was extmded into 3 denier fibers. The extmded fibers were crimped, oven-dried, and then treated by kiss-coating using a conventional smooth cylinder-type coating apparatus with a mixture of 205.6 kg of a hydrophilic antistatic lubricant Sipo Lube GS-1031 commercially available from Synthetic Industries, Inc. , Chickamauga, GA and 36.4 kg of SCOTCHGARD brand fabric protector, FC-359, a fluorochemical mixture commercially available from 3M, St. Paul, MN. The fiber was then cut as in Example 1 into staple fibers 3.81 cm and 4.76 cm in length. Some of the 3.81 cm fiber was processed into nonwoven cast padding using a conventional Randoweb Equipment by Astro-Form Corporation, Danielson, CT. Padding rolls 7.62 cm and 10.2 cm wide were prepared and evaluated using the modified AATCC Test Method described above. The surface energy of the fibers was found to be in the range of 26.4 to 27.3 ergs/cm. Some of the 4.76 cm fiber was spun into 20 (cotton count) single yam using well-known processes by Southern Industrial, Rossville, GA. The yam was then knitted into stockinette rolls 5.08 cm and 7.62 cm wide by Balfour, Inc. , Rockwood, TN, using commercially available circular Rib-Knit Equipment. The stockinette was evaluated using the modified AATCC Test Method and found to have a surface energy in the range 26.4 to 27.3 erg/cm.

Claims: CLAIMS 1. A water repellant orthopedic dressing comprising a soft, smooth, conformable, air-permeable, hydrophobic fabric made of polymeric fibers wherein the fibers are an extmded blend of a thermoplastic polymer and a fluorochemical oxazolidinone. 2. The dressing of claim 1 wherein the polymer is selected from the group consisting of polyethylene, polypropylene and polyester. 3. The dressing of claim 1 wherein the oxazolidinone is a compound of the formula 4. The dressing of claim 1 wherein the fabric has a surface energy of less than about 40 erg/cm 2 . 5. The dressing of claim 1 wherein the fabric has a surface energy of less than about 30 erg/cm 2 . 6. The dressing of claim 1 wherein the dressing is a nonwoven or knitted fabric. 7. The dressing of claim 1 further comprising contacting the surface of the fibers with a hydrophilic antistatic lubricant and a water repellent fluorochemical. 8. A method for manufacturing an orthopedic dressing comprising knitting or weaving fibers of an extmded blend of a polymer and a fluorochemical oxazolidinone into an orthopedic dressing. 9. An orthopedic splint comprising a multilayer resin impregnated fiberglass tape covered on at least one major surface with a padding comprising a soft, smooth, conformable, air-permeable, hydrophobic fabric of claim 1. 10. An orthopedic splint comprising a multilayer resin impregnated fiberglass tape covered on a first major surface with a fluorochemical treated non-woven fabric and covered on second major surface with a padding comprising a soft, smooth, conformable, air-permeable, hydrophobic fabric of claim 1.

Inventors: CAMPAGNA ANTHONY J, ERSFELD DEAN A, SANDVIG TIMOTHY C, SCHOLZ MATTHEW T, CAMPAGNA, ANTHONY, J., ERSFELD, DEAN, A., SANDVIG, TIMOTHY, C., SCHOLZ, MATTHEW, T.
Applicants: CAMPAGNA ANTHONY J, ERSFELD DEAN A, MINNESOTA MINING & MFG, SANDVIG TIMOTHY C, SCHOLZ MATTHEW T, CAMPAGNA, ANTHONY, J., ERSFELD, DEAN, A., MINNESOTA MINING AND MANUFACTURING COMPANY, SANDVIG, TIMOTHY, C., SCHOLZ, MATTHEW, T.
Application year: 1994
Main classification: A61L15
IPC codes: A61F5, A61F13, A61L15, C08K5, D01F6